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Our new patio is crazing. What should we do?

Q:    I would like to ask a question concerning a concrete patio we recently had poured. We had a contractor pour a 1000 ft.2 patio which was 3.5-4 inches thick and divided into 9'x9' squares with a rock salt finish, no wire or rebar, approximately 95-100 degrees by the end of the finishing. He left us to cure the concrete by spraying with water. We started spraying it about 2-3 hours after finishing and wetted it down for the next seven days about every 1 to 2 hours. It was about 95-100 degrees at the high of the day for the next two weeks.
The finish now looks like what I think may be crazing. When sprayed with water little cracks become very apparent, originating at the holes made from the salt pushed into the surface. It looks something like a shattered window pane put back together. After about 10 minutes with water on it, the cracks disappear (looks like water soaking in) and the whole surface looks darker grew. If you look very close you can still see little lines where the cracks were eye catching before the water soaked in. At the radius edges, when dry, tiny cracks are visible, some continue through the thickness of the slab and extend 5 or so inches along the top surface.
Can you tell us what you think the underlying problem is with the concrete and do you think it will last (will these little tiny surface cracks propagate through the thickness of the slab? The concrete is about 7 weeks old. If it will last is there anything that can be done to hide the non-uniform look when it initially gets wet, such as a sealer or acid stain?


A:     I would agree with your diagnosis of crazing, especially since the crazing pattern is most obvious when the concrete surface is wet.
The good news is that crazing is rarely anything other than a cosmetic problem, so I do not think that you have a problem as far as the slab being able to serve its intended purpose as a patio. Normally, crazing will not lead to further slab cracking, and the crazing cracks will not spread or become larger.
The bad news is that you will probably have to live with the appearance as I do not think that either sealing or acid staining will do anything to hide the crazing.
Just for future knowledge: Water curing of a slab is still the best curing method around, but only when the slab surface is kept wet continually. Spraying the slab, then letting it dry or even partially dry before spraying again can actually induce thermal cracking because the slab is being allowed to heat up and dry out, then quickly cooled off and saturated by the spraying. If you can not pond the slab surface, you need to let a sprinkler run continuously to keep the slab at a uniform temperature and moisture.